1. Field of the Invention
The present invention relates to an ultra-dry fog box, for use in providing a fog along a dimension. In particular, the present invention relates to an ultra-dry fog box for the emission of a fog along a dimension, comprising a fog retention enclosure, having a length along which a fog is desired. The enclosure comprises at least one emission opening along its length for the emission of a substantially uniform fog. At least one inlet passage is located in the enclosure, permitting the intake of ambient air into the enclosure. An internal circuitous path is located within the enclosure, comprising a flow path in fluid communication between the inlet passage and the emission opening and including, at least in part, a near-reversal of flow from a gravitational direction. The enclosure further includes a means for creating a flow of ambient air into the enclosure through the inlet passage, and out of the enclosure through the emission opening. At least one pin jet nozzle is provided in the enclosure and is adapted for use in providing a fog. The pin jet nozzle is located proximate to the inlet passage or within the enclosure so that fluid discharged from the pin jet nozzle enters the flow path.
In a preferred embodiment, the device of the present invention provides an ultra-dry fog box for the emission of a fog along a dimension, including a fog retention enclosure having a length along which a fog is desired. The enclosure comprises at least one emission opening along its length for the emission of a substantially uniform fog, and at least one inlet passage permitting the intake of ambient air into the enclosure. The enclosure further includes an internal circuitous path comprising a flow path in fluid communication between the inlet passage and the emission opening, and including, at least in part, a near-reversal of a flow from a gravitational direction. The enclosure further includes means for creating a flow of ambient air into the enclosure through the inlet passage and out of the enclosure through the emission opening. The enclosure further includes at least one improved pin jet nozzle which is adapted for use in providing a fog consisting essentially of fluid particles having a diameter of less than fifty micrometers. The nozzle comprises a base portion which includes a means for connecting the nozzle to a pressurized hydraulic system, a means for receiving fluid from the hydraulic system, and an orifice component. The orifice component includes an inlet adapted to receive fluid from the hydraulic system, an outlet orifice for the release of fluid from the system in the form of a jet, and a delivery channel which is adapted to convey fluid from the inlet to the outlet orifice. The nozzle further comprises a pin portion which includes a support and centering means, and an impingement pin member mounted upon the support and centering means which is positioned over the outlet orifice, wherein the impingement pin member has an impingement face in the path of the fluid jet which is substantially similar in dimension to the diameter of the fluid jet. Further, the nozzle includes a nozzle insert which includes an insert member comprising a hollow, generally cylindrical insert which is adapted to be held firmly within the outlet orifice of the base portion, and an orifice member which is held firmly within the generally cylindrical insert member. The orifice member comprises a wear-resistant material, a central orifice with a diameter of from about three one-thousandths of an inch (0.003 inch) to about fifteen one-thousandths of an inch (0.015 inch), and a high degree of concentricity, with a variance in the concentricity of the central orifice of less than five ten-thousandths of an inch (0.0005 inch). The pin jet nozzle is located proximate to the inlet passage or within the enclosure so that fluid discharge from the pin jet nozzle will enter the flow path.
In a still further preferred embodiment, these devices of the present invention further provide at least one mesh filter disposed within said flow path for fluid particles.
2. Description of Related Art
Evaporative cooling systems have been employed in various applications for a number of years. Such systems typically involve a pressurized fluid, usually water, escaping through a small orifice and impinging on a proximate surface. The force of the pressurized stream against the proximate surface causes the fluid to disperse into minute particles creating a localized fog. A fog differs from a mist, although the terms are often used imprecisely. As used herein, a fog contains small droplets which evaporate from the air rather than falling to cause a localized wetting. Fogs are typically used for cooling, and sometimes, for humidification. A mist, as used herein, contains larger particles which fall to create a localized wetting, and are typically used more for providing irrigation.
Because of the difficulty in precisely cutting the small diameter orifice and delivery channel, such prior art nozzles have typically been formed from brass and other relatively soft metals because of the difficulty in working. Recently, some nozzles have been produced in stainless steel, however, such nozzles still follow the design of previous nozzles.
The short delivery channels of the prior art appeared to be necessary because of the limitations of metalworking. Cutting a narrow orifice, typically on the order of six one-thousandths of an inch (0.006 inch), is typically done with a pin drill, usually a stationary drill which engages rotating work. The depth which can be achieved with such a metalworking procedure, typically no greater than fifteen-thousandths of an inch (0.015 inch), is chiefly a function of how well the drill bit can be supported during the metal working process.
Further, and perhaps more important to the present invention, the nature of the metalworking employed to cut the orifice and delivery channel is such that the concentricity of the orifice and the integrity of the orifice and channel walls is difficult to maintain. The drilling operation is known to gouge and scar the interior surface (of the delivery channel and leave an imprecise mouth to the orifice itself.
These problems were addressed in U.S. Pat. No. 4,869,430 to Good. That reference teaches the use of an insert cut from a length of stainless steel surgical tubing. While this reference overcomes many of the difficulties of the prior art, the internal diameter of such tubing is not always dimensionally accurate, and the metalworking of the cut ends of the tubing sometimes distorts the mouth of the orifice. Further, the extrusion process which draws such tubing is primarily concerned with the outside diameter of the finished tubing, and the inside diameter is often imprecise, with fluting and a lack of concentricity being common problems. Such fluting can cause collection of debris, while a lack of concentricity causes a variance in spray patterns. In either case, the variable flow which resulted from piece to piece variations meant that system flow volumes could not be accurately predicted.
Even with the improvements taught in the Good reference, however, it has been difficult, if not impossible, to predict the flow requirements of a system where a plurality of nozzles of different flow rates are employed. Such a situation has rendered it difficult to design efficient spray patterns and regular flow levels.
A pin-jet nozzle is used in a hydraulic system in which the water is pressurized to about 350 to over 1,000 pounds per square inch. At that pressure a thin, substantially-coherent stream of water is forced out through an orifice which is a hole approximately six one-thousandths of an inch in diameter and against an external impingement pin, which is also about six one-thousandths of an inch in diameter, although it is common for larger size impingement pins to be employed.
This creates droplets that are small, small enough that such droplets are essentially unaffected by gravity because of their increased surface area in proportion to their volume. Water droplets of such small dimension evaporate in the air rather than causing localized wetting. With the evaporation of each droplet, it's heat of vaporization is removed from the ambient air, reducing the ambient air temperature. An array of 200 to 300 of these nozzles can cool a large area, even an outdoor area.
Wetting was always the problem with prior art evaporative cooling systems. Not only does wetting mean that cooling isn't being done efficiently, wetting can actually be harmful in many applications, by leading to mildew and mold, and damaging perishables, etc. A nozzle that puts out any significant number of large particles causes wetting, limiting the uses of the cooling system. Wear was one reason why nozzles did not perform in service, but manufacturing irregularities have been a much greater factor. The wear characteristics of a nozzle were unimportant if the nozzle could not be put into service in the first place.
A substantially uniform fog of small particle size has recently become practical, as taught by U.S. patent application Ser. No.: 08/474,947, filed Jun. 7, 1995, claiming priority of application Ser. No.: 07/919,164, filed Jul. 23, 1992, issued Apr. 15, 1997, as U.S. Pat. No. 5,620,142, the teachings of which reference are hereby incorporated by reference, as if fully set forth herein.
With a fog of such small particle size, it has become possible to utilize a water fog for theatrical effects and amusement displays, as well as cooling in environments where people are present. Where fog is employed for effects, however, it is the quantity and opacity of the fog which is generally important, not its cooling capacity. When several nozzles of the type taught in this reference are brought into close proximity to create a fog for theatrical purposes, however, a fog with larger particle size water droplets results. While the reason for this remains conjectural, it is believed that the relatively high kinetic energy of the small water particles issuing from each independent nozzle causes collisions of the particles with the particles from adjacent nozzles, resulting in larger droplet size. As such, the benefits of small particle size fogs have not heretofore been achieved by closely-spaced arrays of these nozzles.